Nowadays, in a wide range of fields, including the fields of medical and food products, the operations of mixing, granulating and sizing powdery granular bodies are performed. The grain size adjustment work that is performed in a product production process is one of the important unit operations for improving fluidization of a fluidized drying process and improving the handling process.
Here, in a conventionally-used powder based granules disintegrating and sizing device, granular size control was performed using a screen. Therefore, there was a possibility that the screen would become worn and damaged by continuous use and that worn particles or damaged pieces of the screen are mixed into the produced powder based granules. Also, in the case of a wet material, depending on the property of the processed substance, the screen was clogged when the substance adhered thereto, and the processed substance was kneaded inside the screen. Furthermore, there was a disadvantage that grains of an appropriate grain size also were disintegrated by impact force of a granulating blade, whereby a large number of fine particles were generated, resulting in poor yields.
Therefore, the present applicant has first developed a powder based granules disintegrating and sizing device in which a screen is not used, and applied for a patent [see Japanese Published Unexamined Patent Application No. 2000-117131 (“Patent Literature 1” hereinafter) and WO 2004/085069A1 (“Patent Literature 2” hereinafter)].
This powder based granules disintegrating and sizing device is a powder based granules disintegrating and sizing device for sizing wet or dried material, which is supplied from a material feeding port, through a predetermined accumulation region, wherein: a rotating body and an opposed surface portion that faces the rotating body to have a predetermined space there between are provided to form a gap area within a casing main body configuring the device; the gap area is constituted to be a grain size adjusting area that allows particles fitting to the predetermined set gap to pass and does not allow passage of particles that are not fitting to the predetermined set gap; and the particles that cannot pass through the gap area are brought into contact with the opposed surface portion at an inlet or a surface area portion of the gap area in cooperation with the rotation of the rotating body and disintegrated so as to be able to pass through the gap area and then be discharged from a discharge port.
Here, the gap area is provided with the surface area portion or a line area portion, which sets the space between the rotating body and the opposed surface portion as a narrowest gap portion, and the narrowest gap portion is configured to disintegrate the particles in the vicinity thereof.
Specifically, in the powder based granules disintegrating and sizing device described in Patent Literature 1, the rotating body is formed into a substantially conical shape having a rotation shaft in a vertical direction, the casing main body is formed into a substantially hollow conical shape, the accumulation region of the powder based granules is configured by an inner wall of the casing main body and a circumferential surface of the rotating body, and the narrowest gap portion is configured by a lower end circumferential edge of the rotating body and the inner wall of the casing main body.
Moreover, in the powder based granules disintegrating and sizing device described in Patent Literature 2, a casing main body has therein a horizontally fitted drive shaft, a plurality of circular plates fixedly supported at intervals by the drive shaft, and stators which are arranged so as to be opposed to plate surfaces at lower circumferential edge portions of the circular plates and each of which has an inclined surface that narrows a gap between adjacent plate surfaces toward circumferential edges of the plate surfaces, wherein the plate surfaces of the circular plates and the inclined surfaces of the stators form gap portions where a powder based granules accumulates, and wherein disintegrating and sizing portions are configured by narrowest gap portions formed between the circumferential edges of the circular plates and the stators.
However, in the powder based granules disintegrating and sizing device described in Patent Literature 1, the narrowest gap portion that is formed by the lower circumferential edge of the substantially conical rotating body and the inner wall of the casing main body is in the form of a single line forming a circle. For this reason, a large disintegrating and sizing area cannot be obtained, and thus there is a problem that the diameter of a lower part of the rotating body needs to be increased in order to obtain a large disintegrating and sizing area, which leads to an increase in the size of the device.
Also, in the powder based granules disintegrating and sizing device described in Patent Literature 2, because the stators are fitted only on the lower side of the circular plates, disintegrating and sizing actions are not performed on the upper side of the circular plates, which makes the device inefficient. Moreover, the powder based granules to be processed is supplied from the upper side of the circular plates, but it is difficult to allow the powder based granules to enter the upper side of the circular plates because the powder based granules is bounced by the centrifugal force of the circular plates. In addition, the problem when processing a highly wet material is that processed substances adhere to the disintegrating and sizing portions (narrowest gap portions), the vicinity of the feeding port, the vicinity of the discharge portion and the like, whereby stable operation cannot be performed.